Three way catalyst comprising extruded solid body

ABSTRACT

A three way catalyst comprises an extruded solid body comprising: 10-100% by weight of at least one binder/matrix component; 5-90% by weight of a zeolitic molecular sieve, a non-zeolitic molecular sieve or a mixture of any two or more thereof; and 0-80% by weight optionally stabilised ceria, which catalyst comprising at least one precious metal and optionally at least one non-precious metal, wherein: (i) the at least one precious metal is carried in one or more coating layer(s) on a surface of the extruded solid body; (ii) at least one metal is present throughout the extruded solid body and at least one precious metal is also carried in one or more coating layer(s) on a surface of the extruded solid body; or (iii) at least one metal is present throughout the extruded solid body, is present in a higher concentration at a surface of the extruded solid body and at least one precious metal is also carried in one or more coating layer(s) on the surface of the extruded solid body.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is the U.S. National Phase application of PCTInternational Application No. PCT/GB2011/050158, filed Feb. 1, 2011, andclaims priority of U.S. Provisional Patent Application No. 61/300,279,filed Feb. 1, 2010, the disclosures of both of which are incorporatedherein by reference in their entireties for all purposes.

FIELD OF THE INVENTION

The present invention relates to three-way catalysts comprising anextruded solid body for use in treating exhaust gas emissions frominternal combustion engines particularly for stationary source andmobile i.e. vehicular (automobile) applications.

BACKGROUND OF THE INVENTION

US 2002/0183191 discloses a three-way catalyst comprising azeolite/alumina composite catalyst support exhibiting a modulus ofrupture of at least 750 psi and having a zeolite with a silica/aluminaratio of at least 300, which catalyst support is impregnated with anoble metal selected from the group consisting of platinum, rhodium,iridium and palladium. The three-way catalyst has high cell density,thin walls and no washcoat. In one embodiment, the catalyst supportcontains optionally stabilised zirconia in addition to the zeolite andalumina. The zirconia dopant can include cerium oxide in amounts up to80 wt % based on the total zirconium amount. However, no Exampleincluding optionally doped zirconia is provided.

US '191 explicitly excludes washcoating with a catalyst-containingslurry to avoid a reduction in the channel size of a honeycomb andincreased backpressure. Furthermore, the use of silica binder isexcluded because of incompatibility between silica and platinum groupmetals. Hence, gamma alumina is used as the binder. However, in thecomparison examples provided, the three-way catalyst performance(measured as light off temperature for converting CO, NO_(x) andhydrocarbons) of catalysts according to the invention, particularly for50:50 and 40:60 weight ratios of zeolite:gamma alumina, compare poorlywith comparative examples comprising an alumina-only extruded support ora zeolite/silica binder-based support.

U.S. Pat. No. 5,772,972 discloses an automotive catalyst system fortreating internal combustion engine exhaust gases. The system comprisesa hybrid system of a zeolite hydrocarbon trap and a palladium-basedthree-way catalyst material carried on a substrate monolith. In oneembodiment, the three-way catalyst is layered on an extruded zeolitesubstrate monolith. However, no specific Example including an extrudedzeolite substrate monolith is provided.

EP 1739066 discloses a honeycomb structure comprising multiple honeycombunits having multiple through holes; and a seal layer that joinshoneycomb units with each other via respective closed outer faces of thehoneycomb units where the through holes are not open. The honeycomb unitincludes at least inorganic particles, inorganic fibers and/or whiskers.The inorganic particles exemplified are alumina, titania, silica andzirconia; the inorganic fibres exemplified are silica alumina fibres;and the inorganic binders exemplified are silica sol, alumina sol,sepiolite and attapulgite. A catalyst component can be carried on thehoneycomb structure. The catalyst component may include at least onetype selected among noble metals including platinum, palladium andrhodium, alkali metals such as potassium and sodium, alkaline earthmetal e.g., barium and oxides. The honeycomb structure can be used as acatalytic converter e.g., a three-way catalyst or a NO_(x) storagecatalyst for conversion of the exhaust gas of vehicles.

SUMMARY OF THE INVENTION

We have now developed a family of three-way catalysts comprising anextruded solid body coated with at least one precious metal withparticular application in the field of exhaust gas aftertreatment ofinternal combustion engine exhaust gas. Such exhaust gases may resultfrom stationary source emissions, but they have been developed for usein particular for treating mobile sources of emissions, such aspassenger cars, trucks and buses.

According to one embodiment, the invention provides a three-way catalystcomprising an extruded solid body comprising: 10-95% by weight of atleast one binder/matrix component; 5-90% by weight of a zeoliticmolecular sieve, a non-zeolitic molecular sieve or a mixture of any twoor more thereof; and 0-80% by weight optionally stabilised ceria,

which catalyst comprising at least one precious metal and optionally atleast one non-precious metal, wherein:

(i) the at least one precious metal is carried in one or more coatinglayer(s) on a surface of the extruded solid body;

(ii) at least one metal is present throughout the extruded solid bodyand at least one precious metal is also carried in one or more coatinglayer(s) on a surface of the extruded solid body; or

(iii) at least one metal is present throughout the extruded solid body,is present in a higher concentration at a surface of the extruded solidbody and at least one precious metal is also carried in one or morecoating layer(s) on the surface of the extruded solid body.

An advantage of the present invention is that by removing catalyticcomponents that are often used in catalytic coatings, the number ofcoatings can be reduced, e.g. from two layers to one layer. This hasbenefits in reducing backpressure in an exhaust system, increasing theefficiency of the engine.

The present invention has a number of particular advantages overcatalysts according to US '191 described hereinabove. Whilst theinventors acknowledge that by coating a extruded body that some of thedrawbacks mentioned in US '191 may be encountered in certainconfigurations of three-way catalysts according to the presentinvention, such drawbacks are significantly outweighed by thefundamental improvement in catalytic activity, particularly relative to50:50 and 40:60 by weight zeolite:alumina embodiments disclosed in US'191. Furthermore, the present invention is not restricted to use ofnon-silica binders. Additionally, lower silica:alumina ratio molecularsieves can be used in the present invention which allows the molecularsieves to be ion-exchanged to a greater extent with metals that promoteHC adsorption (ion exchange sites are removed by increasingsilica:alumina ratio) for reducing cold-start HC emissions.

Also it is possible to increase the volume of active components in anextruded solid body relative to a coating on an inert substratemonolith. This increased catalyst density has advantages for long termdurability and catalyst performance, which is important for on-boarddiagnostics.

BRIEF DESCRIPTION OF THE FIGURES

In order that the invention may be more fully understood, the followingExamples are provided by way of illustration only and with reference tothe accompanying drawings in which:

FIG. 1 is a graph showing the experimental test procedure for analysingthe activity of a three-way catalyst according to Example 2;

FIG. 2 is a graph comparing the cumulative hydrocarbon at outlet intesting according to Example 4 of a three-way catalyst according toExample 2 and of a Comparative three-way catalyst according to Example3;

FIG. 3 is a graph comparing the pore volume and porosity of variousV₂O₅/WO_(x)-TiO₂ filter materials prepared using various pore modifiersrelative to a Reference product used in a flow-through configuration;and

FIG. 4 is a graph plotting the pore volume against pore radius for anumber of pore modifiers relative to the V₂O₅/WO_(x)-TiO₂ Reference anda commercially available wallflow filter substrate.

DETAILED DESCRIPTION OF THE INVENTION

“On board diagnostics” (OBD) in the context of a motor vehicle is ageneric term to describe the self diagnostic and reporting capability ofthe vehicle's systems provided by a network of sensors linked to asuitable electronic management system. Early examples of OBD systemswould simply illuminate a malfunction indicator light if a problem weredetected, but it provided no information on the nature of the problem.More modern OBD systems use a standardised digital connection port andare capable of providing information on standardised diagnostic troublecodes and a selection of real-time data, which enable rapid problemidentification and resolution of a vehicle's systems.

Current OBD requirements require that a driver must be notified in caseof a malfunction or deterioration of the emission system that wouldcause emissions to exceed mandatory thresholds. So, for example, the OBDlimits for passenger petrol (gasoline) vehicles, the Euro 4 limits are:CO—3.2 g/km; HC—0.4 g/km; NO—0.6 g/km; and PM—no limit.

Future vehicular emissions legislation, especially in US and Europe,requires higher sensitivity in diagnostic function so as continuously tomonitor the ability of an exhaust system aftertreatment catalyst to meetthe emission legislation. For example, the current draft OBD limits forpositive ignition (gasoline) passenger vehicles: CO—1.9 g/km; NMHC—0.25g/km; NO—0.54 g/km; and PM—no limit.

In the U.S., it is understood that the OBD II legislation (Title 13,California Code Regulations, Section 1968.2, Malfunction and DiagnosticSystem Requirements for 2004 and Subsequent Model-Year Passenger Cars,Light-Duty Trucks and Medium-Duty Vehicles and Engines) for catalystmonitoring of gasoline/spark ignited engines requires a malfunctionsignal where the average Federal Test Procedure (FTP) test for NMHCconversion efficiency of a monitored portion of a catalyst system fallsbelow 50%.

Extruded solid bodies according to the present invention generallycomprise a unitary structure in the form of a honeycomb havinguniform-sized and parallel channels extending from a first end to asecond end thereof. Generally, the channels are open at both the firstand second ends—a so-called “flow through” configuration. Channel wallsdefining the channels are porous. Typically an external “skin” surroundsa plurality of the channels of the extruded solid body. The extrudedsolid body can be formed from any desired cross section, such ascircular, square or oval. Individual channels in the plurality ofchannels can be square, triangular, hexagonal, circular etc. Channels ata first, upstream end can be blocked e.g. with a suitable ceramiccement, and channels not blocked at the first, upstream end can also beblocked at a second, downstream end to form a so-called wall-flowfilter. Typically, the arrangement of the blocked channels at the first,upstream end resembles a chequer board with a similar arrangement ofblocked and open downstream channel ends.

It is clear that the honeycomb structure disclosed in EP 1739066 has aThermal Shock Parameter (TSP) too low to be used in a single unitaryextrudate, because the honeycomb structure comprises an assembly ofindividual honeycomb units cemented together. This, arrangement, alsoseen in commercially available silicon carbide honeycombs, is designedto avoid catastrophic catalyst substrate failure due to inter aliathermal shock as a result of a relatively high Coefficient of ThermalExpansion (CTE) of the extruded material. However, the manufacture of ahoneycomb structure from individual honeycomb units is complicated,laborious, time consuming and expensive and increases the number ofpossible physical failure modes, e.g. at the cement bonds, compared witha single piece extrusion. A more complete explanation of TSP and CTE canbe found in “Catalytic Air Pollution Control—Commercial Technology”,Second Edition, R. M. Heck et al., John Wiley & Sons, Inc., New York,2002 Chapters 7 (in relation to flowthrough monoliths) and 9 (forwall-flow filters).

Accordingly, the extruded solid body of the catalyst according to theinvention may preferably have an axial Thermal Shock Parameter (TSP) anda radial TSP sufficient to avoid radial cracks and ring cracks in theextruded solid body when used for treating exhaust gases from astationary or mobile source of emissions. In this way the extruded solidbody can be formed from a single unitary extrudate. For extruded solidbodies having a particularly large cross-section, it may still benecessary to extrude segments of the extruded solid body for cementingtogether. However, this is because of difficulties in processingextrudates of such a large cross section, or because of limitations inthe size of the extrudate die tooling. Taken individually, however, eachsegment of the whole catalyst would meet the functional limitation thatthe axial TSP and the radial TSP are sufficient to avoid radial cracksand ring cracks in the individual extruded solid body segments when usedfor treating exhaust gases from a stationary or mobile source ofemissions. In one embodiment the radial TSP is >0.4 at 750° C., suchas >0.5, >0.6, >0.7, >0.8, >0.9, or >1.0. At 800° C., the radial TSP isdesirably also >0.4 and, particularly for three-way catalysts (whichexperience higher temperatures in use) the TSP at 1000° C. is preferably>0.8.

The CTE of wall-flow filters is preferably 20×10⁻⁷/° C. in order to beformed from a one-piece extrudate.

In embodiments, the at least one binder/matrix component can be selectedfrom the group consisting of cordierite, nitrides, carbides, borides,intermetallics, lithium aluminosilicate, a spinel, an optionally dopedalumina, a silica source, titania, zirconia, titania-zirconia, zirconand mixtures of any two or more thereof.

Spinels can be MgAl₂O₄ or the Mg can be partially replaced by a metalfrom the group consisting of Co, Zr, Zn or Mn. In embodiments thecontent of MgO in the MgAl₂O₄ relative to Al₂O₃ can be from 0.8 to 2.5,with values of <1.0 preferred.

The alumina binder/matrix component is preferably gamma alumina, but canbe any other transition alumina, i.e. alpha alumina, beta alumina, chialumina, eta alumina, rho alumina, kappa alumina, theta alumina, deltaalumina, lanthanum beta alumina and mixtures of any two or more suchtransition aluminas.

It is preferred that the alumina is doped with at least onenon-aluminium element to increase the thermal stability of the alumina.Suitable alumina dopants include silicon, zirconium, barium, lanthanidesand mixtures of any two or more thereof. Suitable lanthanide dopantsinclude La, Ce, Nd, Pr, Gd and mixtures of any two or more thereof.

Sources of silica can include a silica, a silica sol, quartz, fused oramorphous silica, sodium silicate, an amorphous aluminosilicate, analkoxysilane, a silicone resin binder such as methylphenyl siliconeresin, a clay, talc or a mixture of any two or more thereof.

Of this list, the silica can be SiO₂ as such, feldspar, mullite,silica-alumina, silica-magnesia, silica-zirconia, silica-thoria,silica-berylia, silica-titania, ternary silica-alumina-zirconia, ternarysilica-alumina-magnesia, ternary-silica-magnesia-zirconia, ternarysilica-alumina-thoria and mixtures of any two or more thereof.Alternatively, the silica can be derived from calcining tetramethylortho silicate (TMOS) added to the extrusion composition.

Suitable clays include fullers earth, sepiolite, hectorite, a smectite,a kaolin and mixtures of any two or more thereof, wherein the kaolin canbe chosen from subbentonite, anauxite, halloysite, kaolinite, dickite,nacrite and mixtures of any two of more thereof; the smectite can beselected from the group consisting of montmorillonite, nontronite,vermiculite, saponite and mixtures of any two or more thereof; and thefullers earth can be montmorillonite or palygorskite (attapulgite).

Inorganic fibres are selected from the group consisting of carbonfibres, glass fibres, metal fibres, boron fibres, alumina fibres, silicafibres, silica-alumina fibres, silicon carbide fibres, potassiumtitanate fibres, aluminum borate fibres and ceramic fibres.

Suitable molecular sieves for use in the present invention are thosecapable of adsorbing unburned hydrocarbons following cold-start of anautomobile engine and desorbing adsorbed hydrocarbons at above ambienttemperature, e.g. when an associated precious metal-based three-waycatalyst component has reached a desired light-off temperature for e.g.CO and HC oxidation or NO_(x) reduction. Such molecular sieves aregenerally not those having an 8-ring pore opening structure as itslargest pore opening structure, sometimes called “small pore” molecularsieves. Preferred molecular sieves are medium pore (maximum 10-ring poreopening structure), large pore (maximum 12-ring pore opening structure)or oven meso pore (>12-ring pore opening structure) molecular sieves.

The or each zeolitic molecular sieve or the or each non-zeoliticmolecular sieve can be selected from the framework type code ABW, AEL,AET, AFG, AFI, AFO, AFR, AFS, AFY, AHT, AST, ASV, ATN, ATO, ATS, ATV,AWO, AWW, BCT, BEA, BEC, BIK, BOF, BOG, BPH, BRE, BSV, CAN, CAS, CFI,CGF, CGS, —CHI, —CLO, CON, CZP, DAC, DFO, DOH, DON, EMT, EON, ESV, ETR,EUO, EZT, FAR, FAU, FER, FRA, GIU, GME, GON, HEU, IFR, IMF, ISV, ITH,ITR, IWR, IWS, IWV, IWW, JBW, JRY, LAU, LIO, -LIT, LOS, LOV, LTF, LTL,LTN, MAR, MAZ, MEI, MEL, MEP, MFI, MFS, MOR, MOZ, MRE, MSE, MSO, MTF,MTN, MTT, MTW, MWW, NAB, NAT, NES, NON, NPO, OBW, OFF, OSI, OSO, —PAR,PON, —RON, RRO, RSN, RTE, RUT, RWR, RWY, SAO, SAS, SBE, SBS, SBT, SFE,SFF, SFG, SFH, SFN, SFO, SFS, SGT, SOD, SOF, SOS, SSF, SSY, STF, STI,STO, STT, STW, —SVR, SZR, TER, TOL, TON, TUN, UOS, UOZ, USI, UTL, VET,VFI, VSV, WEI or —WEN as defined by the Structure Commission of theInternational Zeolite Association and mixtures of any two or morethereof.

Preferred zeolitic and non-zeolitic molecular sieves are selected fromthe group consisting of BEA, FAU, FER, MFI, MFS, MOR, STI, SZR andmixtures of any two or more thereof.

Particularly preferred zeolitic or non-zeolitic molecular sieves areselected from the group consisting of BEA, FER, MFI, STI and mixtures ofany two or more thereof. Particularly preferred zeolitic molecularsieves are ZSM-5, beta, ferrierite and mixtures of any two or morethereof.

Although natural zeolitic molecular sieves can be used in the presentinvention, we prefer synthetic aluminosilicate zeolitic molecular sievehaving a silica-to-alumina ratio of 10 or greater, for example 15 to150, 20 to 60 or 25 to 40 for improved thermal stability.

In an alternative embodiment, the zeolitic molecular sieve or thenon-zeolitic molecular sieve is an isomorph containing one or moresubstituent framework metal. In this embodiment, the or each substituentframework metal can be selected from the group consisting of As, B, Be,Ce, Co, Cu, Fe, Ga, Ge, Li, Mg, Mn, Zn and Zr, with Ce, Cu and Fe.Again, preferred isomorphic zeolitic or non-zeolitic molecular sievescan be selected from the group consisting of BEA, FER, MFI, STI andmixtures of any two or more thereof, with BEA including Fe in itsframework particularly preferred. It will be understood that the processof manufacturing such isomorphs containing one or more substituentframework metal, the or each metal may be present in the final producteither solely in the framework or in the framework and ion-exchanged.

Silica-to-alumina ratios in isomorphs containing one or more substituentframework metal can be >25, such as 30 to 100 or 40 to 70. By contrast,the isomorph can have a silica-to-framework metal ratio of >20, such asfrom 30 to 200 or 50 to 100.

In a preferred embodiment, the non-zeolitic molecular sieve is analuminophosphate, including AlPOs, metal substituted AlPOs (MeAlPOs),silicoaluminophosphates (SAPOs) or a metal substitutedsilicoaluminophosphates (MeAPSOs).

Silica-to-alumina ratios of the aluminophophates are generally muchlower than aluminosilicate zeolites sharing the same framework typecode. Typically, the silica-to-alumina ratio of aluminophosphates is<1.0, but can be <0.5 or even <0.3.

The ceria component can be optionally stabilised with at least onenon-cerium element to increase the thermal stability of the ceria.Suitable ceria stabilisers include zirconium, lanthanides and mixturesof any two or more thereof. Lanthanide stabilisers include La, Nd, Pr,Gd and mixtures of any two or more thereof. The CeO₂:ZrO₂ ratio byweight can be e.g., between 80:20 or 20:80. Commercially availablematerials include 30% by weight CeO₂, 63% ZrO₂, 5% Nd₂O₃, 2% La₂O₃; and40% CeO₂, 50% ZrO₂, 4% La₂O₃, 4% Nd₂O₃ and 2% Y₂O₃.

Broadly, the at least one metal can be present: (a) throughout theextruded solid body, i.e. the at least one metal is present in theextrudate composition; (b) present in a higher concentration at asurface of the extruded solid body; and/or (c) carried in one or morecoating layer(s) on a surface of the extruded solid body in features(ii) and (iii) is different from the at least one metal present in eachof the other location(s) at (a), (b) and (c). So the at least one metalcan be present at location (c), (a) plus (c) or (a) plus (b) plus (c).Where the at least one metal is present in (a) and (c) or (a), (b) and(c), the at least one metal in each location can be the same ordifferent.

Where the at least one metal is present in location (a), i.e. throughoutthe extruded solid body, the at least one metal can be associated with azeolitic molecular sieve, a non-zeolitic molecular sieve or a mixture ofany two or more thereof. An example of “associated with” includes beingion exchanged with the zeolitic molecular sieve component, thenon-zeolitic molecular sieve component or either or both of the zeoliticmolecular sieve component and the non-zeolitic molecular sievecomponents in the mixture. It is also possible in mixtures of two ormore molecular sieves to have the at least one metal associated with onemolecular sieve and not the other. For example, a first molecular sievecan be ion-exchanged with copper, dried and calcined and then mixed witha different molecular sieve with no associated additional metal.

It is known that certain associated metals can contribute to HCadsorption with advantage for the present invention. Preferredadsorption promoting metals include Pd and/or Cu, Ag, alkaline earthmetals and alkali metals, e.g. Cs.

Alternatively, one of two molecular sieves in a mixture can beassociated, e.g. ion exchanged, with a first at least one metal and thena second at least one metal can be added to the extrudate composition,i.e. the second at least one metal is not specifically associated withthe second molecular sieve.

Suitable at least one metal(s) to associate with the or each molecularsieve component can be selected individually from the group consistingof a transition metal, a lanthanide or a mixture of any two or morethereof. Suitable transition metals include Group IB metals, Group IVBmetals, Group VB metals, Group VIIB metals and Group VIII metals.Preferably the at least one transition metal is selected from the groupconsisting of Fe, Cu, Ce, Hf, La, Mn, Pt, Au, Ag, In, Rh, V, Ir, Ru, andOs and mixtures of any two or more thereof. The lanthanide metal can beLa, Pr, Ce and mixtures of two or more thereof.

The total metal content in the at least one metal associated with the oreach molecular sieve component is from 0.1 to 20% by weight, such asfrom 1 to 9% by weight.

The at least one metal present: throughout the extruded solid body butnot associated with the or each molecular sieve; in the majority of theat least one metal located at the surface of the extruded solid body; inone or more coating layer(s) on the surface of the extruded solid body;or in the higher concentration at the surface of the extruded solid bodycan be selected from the group consisting of an alkali metal, analkaline earth metal, a transition metal, a lanthanide or a mixture ofany two or more thereof.

Suitable coatings for supporting catalytic metals for use in the presentinvention include one or more of alumina (Al₂O₃), particularlyγ-alumina, silica (SiO₂), titania (TiO₂), ceria (CeO₂), zirconia (ZrO₂),vanadia (V₂O₅), lanthana (La₂O₃) and zeolites. The ceria and alumina canbe optionally stabilised using the same stabilisers as used for theextruded solid body. Suitable catalytic metals include one or more ofthe precious metals (Au, Ag and the platinum group metals, including Pt,Pd and Rh)). Ceria and stabilised ceria is typically included in athree-way catalyst as an oxygen storage component (OSC). In order topromote the HC adsorption activity of the extruded zeolite which hasbeen coated with a precious metal containing washcoat, it can beadvantageous to use a so-called wide-pore supports, e.g. alumina, aswashcoat support for the precious metal (see e.g. U.S. Pat. No.6,110,862, i.e. a catalytic material comprising a platinum group metalcomponent dispersed on a refractory inorganic oxide support phase, thesupport phase comprising a first support material having a pore sizedistribution in which about 98% of the pore volume of the first supportmaterial is provided by pores that have a radius in the range of about30 to 240 Å).

Techniques for locating at least one metal in higher concentration atthe surface of the extruded solid body include impregnation, preferablythickened impregnation, i.e. an impregnation medium thickened with arheology modifier. Drying methods can also be used to concentrate metalsat a surface of the extruded solid body. For example, a so-called “eggshell” technique, where metals are concentrated at the surface can beobtained by drying the impregnated extruded solid body relatively slowlyso that the metals are deposited at the surface by wicking. Particularchoices of salts and pH conditions can also be used to direct metaldeposition, e.g. by determining the isoelectric point of the extrudedsolid body and then using the correct combination of pH and metal saltsto benefit from an electrostatic attraction between cations or anions inthe metal salts and the extruded solid body.

Suitable transition metals include a Group IB metal, a Group IVB metal,a Group VB metal, a Group VIB metal, a Group VIIB metal and a Group VIIImetal. Preferably, the or each transition metal is selected from thegroup consisting of Fe, Ni, W, Cu, Ce, Hf, La, Mn, Pt, Au, Ag, In, V,Ir, Ru, Rh, Os and mixtures of any two or more thereof; lanthanidemetals can be La, Pr or Ce or mixtures of any two or more thereof;alkali metals include K and Cs; and alkaline earth metals can beselected from Ba and Sr.

The total metal content throughout the extruded solid body but notassociated with the or each molecular sieve component; located at thesurface of the extruded solid body; and/or in the higher concentrationat the surface of the extruded solid body can be from 0.1 to 20% byweight, such as from 1 to 9% by weight.

The total metal content of the extruded solid body, i.e. including anymetal associated with the or each molecular sieve, can be from 0.1 to25% by weight, such as from 1 to 15% by weight.

The total metal content of the catalyst as a whole, including one ormore coating layer(s) on a surface of the extruded solid body comprisesat least one metal, can be from 0.1 to 30% by weight, such as from 1 to25% by weight.

Particularly preferred precious metals for use in the one or morecoating layer(s) on the surface of the extruded solid body for promotingthree-way catalytic activity are Pd per se, a combination of Pt and Rh,a combination of Pd and Rh or a combination of Pt, Pd and Rh. Where morethan one precious metal is present, each metal can be disposed in aseparate layer, one or more precious metal can be present in one layerand one or less than all the precious metals can be present in anotherlayer; or all precious metals can be present in each layer but eachlayer can comprise a different ratio of each precious metal to the oreach other precious metal.

In specific examples, the catalyst according to the invention comprisesan extruded solid body comprising:

10-95% by weight of a cordierite, nitrides, carbides, borides,intermetallics, lithium aluminosilicate, an optionally doped alumina, asilica source, titania, zirconia, titania-zirconia, zircon and mixturesof any two or more thereof; 0-80% by weight of spinel;5-90% by weight of a zeolitic molecular sieve, a non-zeolitic molecularsieve or a mixture of any two or more thereof, each optionallycontaining one or more metal;0-80% by weight optionally stabilised ceria; and0-25% by weight inorganic fibres.

The content of the at least one binder/matrix component can be >15% byweight, >20% by weight, >30% by weight, >35% by weight, >40% byweight, >45% by weight, >50% by weight, >55% by weight, >60% byweight, >65% by weight or >70% by weight, >75% by weight, >80% byweight, >85% by weight or >90% by weight.

The content of the spinel can be >10% by weight, >15% by weight, >20% byweight, >30% by weight, >35% by weight, >40% by weight, >45% byweight, >50% by weight, >55% by weight, >60% by weight, >65% by weightor >70% by weight.

The content of the total content of the molecular sieve(s) can be >10%by weight, >15% by weight, >20% by weight, >30% by weight, >35% byweight, >40% by weight, >45% by weight, >50% by weight, >55% byweight, >60% by weight, >65% by weight or >70% by weight, >75% byweight, >80% by weight, >85% by weight or >90% by weight.

The content of the optionally stabilised ceria can be >5% byweight, >10% by weight, >15% by weight, >20% by weight, >30% byweight, >35% by weight, >40% by weight, >45% by weight, >50% byweight, >55% by weight, >60% by weight, >65% by weight or >70% byweight.

The content of the inorganic fibres can be >5% by weight, >10% byweight, >15% by weight or >20% by weight.

In an embodiment the extruded solid body consists essentially of: 10-50%by weight of cordierite, nitrides, carbides, borides, intermetallics,lithium aluminosilicate, a spinel, an optionally doped alumina, a sourceof silica, titania, zirconia, titania-zirconia, zircon and mixtures ofany two or more thereof; 50-90% by weight of a zeolitic molecular sieve,a non-zeolitic molecular sieve or a mixture of any two or more thereof,each optionally containing one or more metal; and 0-25% by weight ofinorganic fibres. This extruded solid body can be arranged as aflow-through substrate monolith or it can be used to make a wall-flowfilter. Preferred embodiments contain inorganic fibres.

Further embodiments can use an extruded solid body consistingessentially of: 10-37% by weight of cordierite, nitrides, carbides,borides, intermetallics, lithium aluminosilicate, an optionally dopedalumina, a spinel, a silica source, titania, zirconia, titania-zirconia,zircon and mixtures of any two or more thereof; 60-88% by weight of azeolitic molecular sieve, a non-zeolitic molecular sieve or a mixture ofany two or more thereof, each optionally containing one or more metal;and 0-20% by weight of inorganic fibers; or: 15-30% by weight ofcordierite, nitrides, carbides, borides, intermetallics, lithiumaluminosilicate, an optionally doped alumina, a spinel, titania,zirconia, titania-zirconia, zircon and mixtures of any two or morethereof; 2-20% by weight of a source of silica; 50-81% by weight of azeolitic molecular sieve, a non-zeolitic molecular sieve or a mixture ofany two or more thereof, each optionally containing one or more metal;and 2-10% by weight of inorganic fibres.

In another embodiment suited for use in three-way catalysts, theextruded solid body can consist essentially of: 10-75% by weight ofcordierite, nitrides, carbides, borides, intermetallics, lithiumaluminosilicate, an optionally doped alumina, a spinel, a silica source,titania, zirconia, titania-zirconia, zircon and mixtures of any two ormore thereof; 5-50% by weight of a zeolitic molecular sieve, anon-zeolitic molecular sieve or a mixture of any two or more thereof,each optionally containing one or more metal; 20-80% by weightoptionally stabilised ceria; and 0-25% by weight of inorganic fibres.Preferred embodiments contain zeolites and inorganic fibres.

In developing extruded solid bodies for use in NO_(x) trap catalystsaccording to the present invention, we have encountered a lack ofstrength in the extruded solid body in the composition: 69% by weight ofCeO₂, and 23% by weight of γ-Al₂O₃ and 8% by weight glass fibres.Current proposals for increasing strength include pre-calcining the CeO₂material to reduce surface loss during calcinations of the “green”extruded solid body; increasing the alumina content to 50%+; changingthe particle size of the alumina (e.g. from commercially availablePural™ to Disperal™) and/or the optionally stabilised ceria; adding aninert binder to increase mechanical stability e.g. a clay; use adifferent alumina e.g. an alumina sol; testing other binder systems e.g.TiO₂ sols, CeO₂ sols; cerium acetate; zirconium acetate; optimising thepH; and adding surface modifiers e.g. aluminium salts or other organicsurfactants. In preliminary tests we have found that the presence ofsilica can affect NO_(x) trap performance. However, research iscontinuing and this option will be further investigated. However, in oneembodiment the content of a source of silica will be reduced or removedaltogether.

Where any of the above extruded solid bodies are made into a wall-flowfilter, the porosity of the wall-flow filter can be from 30-80%, such asfrom 40-70%.

In more specific examples according to the present invention:

-   -   (i) a catalysed soot filter comprises an extruded solid body in        the wall-flow filter configuration consisting essentially of:        15-70% by weight of cordierite, nitrides, carbides, borides,        intermetallics, lithium aluminosilicate, a spinel, an optionally        doped alumina, titania, zirconia, titania-zirconia, zircon and        mixtures of any two or more thereof; 0-20% by weight of a source        of silica; 5-50% by weight of a zeolitic molecular sieve, a        non-zeolitic molecular sieve or a mixture of any two or more        thereof, each optionally containing one or more metal; 20-80% by        weight optionally stabilised ceria; and 0-20% by weight of        inorganic fibres, which extruded solid catalyst body being        coated with one or more layer(s) comprising supported at least        one precious metal and combinations of any two or more precious        metals;    -   (ii) a three-way catalyst comprises an extruded solid body in        the flow-through configuration, consisting essentially of:        15-30% by weight of cordierite, nitrides, carbides, borides,        intermetallics, lithium aluminosilicate, a spinel, an optionally        doped alumina, titania, zirconia, titania-zirconia, zircon and        mixtures of any two or more thereof; 0-20% by weight of a source        of silica; 50-81% by weight of a zeolitic molecular sieve, a        non-zeolitic molecular sieve or a mixture of any two or more        thereof, each optionally containing one or more metal; and 0-20%        by weight of inorganic fibres, which extruded solid catalyst        body being coated with a single layer comprising a mixture of a        majority of γ-alumina and a stabilised ceria supporting        palladium only, a mixture of palladium and rhodium, a mixture of        platinum and rhodium or a mixture of platinum, palladium and        rhodium;

According to a further aspect, the invention provides a process ofmanufacturing a three-way catalyst according to any preceding claim,which process comprising the steps of: forming a solid extruded body bymixing powdered starting materials of: at least one binder/matrixcomponent or a precursor of one or more thereof; zeolitic molecularsieve, non zeolitic molecular sieve or a mixture of any two or morethereof which zeolitic molecular sieve, non-zeolitic molecular sieve ormixture of zeolitic and non-zeolitic molecular sieves being optionallyassociated with at least one metal; an optional optionally stabilisedceria; and an optional at least one metal compound; with optionalinorganic fibers; optionally adding an organic auxiliary agent;processing by mixing and/or kneading in an acid or alkaline aqueoussolution optionally containing a metal salt of at least one metal into aplastic compound to form a mixture; extruding the mixture into acatalyst body, drying the catalyst body and calcining to form a solidextruded body; selecting quantitative proportions of the startingmaterials such that the solid extruded body comprises 10-95% by weightof at least one binder/matrix component; 5-90% by weight of a zeoliticmolecular sieve, a non-zeolitic molecular sieve or a mixture of any twoor more thereof; and 0-80% by weight optionally stabilised ceria, andcoating a surface of the solid extruded body with at least one coatinglayer(s) containing at least one precious metal and optionally alsoimpregnating a surface of the solid extruded body with at least onemetal.

Very generally, the production of an extruded solid body, a binder, anorganic viscosity-enhancing compound and a liquid for converting thematerial by blending into an homogeneous paste are added to thebinder/matrix component or a precursor thereof and optional molecularsieve, optional optionally stabilised ceria, optional inorganic fibresand optional at least one metal compound, and the mixture is compactedin a mixing or kneading apparatus or an extruder. The mixtures haveorganic additives such as binders, plasticizers, surfactants,lubricants, dispersants as processing aids to enhance wetting andtherefore produce a uniform batch. The resulting plastic material isthen moulded, in particular using an extrusion press or an extruderincluding an extrusion die, and the resulting mouldings are dried andcalcined. The organic additives are “burnt out” during calcinations ofthe extruded solid body.

The at least one binder/matrix component is selected from the groupconsisting of cordierite, nitrides, carbides, borides, intermetallics,lithium aluminosilicate, a spinel, an optionally doped alumina, a silicasource, titania, zirconia, titania-zirconia, zircon and mixtures of anytwo or more thereof. An alumina precursor can be used which is aluminiumhydroxide or boehmite. Where an aluminium oxide is used, to ensure thebinding with the aluminium oxide, it is advantageous to add an aqueoussolution of a water-soluble metal salt to the aluminium oxide or theprecursor substance of the aluminium oxide before adding the otherstarting materials.

In embodiments, the silica source can be selected from the groupconsisting of a silica, a silica sol, quartz, fused or amorphous silica,sodium silicate, an amorphous aluminosilicate, an alkoxysilane, asilicone resin binder, a clay, talc or a mixture of any two or morethereof.

In a particular embodiment, the silica source is a silicone resin binderand a solvent for the silicone resin binder is isopropyl alcohol or adibasic ester.

One embodiment of the process according to the present inventioncomprises the step of first admixing an optionally doped alumina or aprecursor thereof with the solution and subsequently admixing thezeolitic molecular sieve, non zeolitic molecular sieve or a mixture ofany two or more thereof and the inorganic fibres.

The organic auxiliary agent for use in the process according to thepresent invention can be one or more selected from the group consistingof a cellulose derivative, an organic plasticizer, a lubricant and awater-soluble resin. Examples of suitable cellulose derivatives includecellulose ethers selected from the group consisting of methylcellulose,ethylcellulose, carboxymethylcellulose, ethylhydroxyethylcellulose,hydroxyethylcellulose, hydroxypropylcellulose,methylhydroxyethylcellulose, methylhydroxypropylcellulose andcombinations of any two or more thereof. Cellulose derivatives increasethe porosity of the final product, which is advantageous for thecatalytic activity of the solid catalyst body. Initially the celluloseswells in the aqueous suspension but is ultimately removed during thecalcining process.

The organic plasticizer for use in the process of the present inventionis selected from the group consisting of polyvinyl alcohol, polyvinylbutyral, an ionomer, acrylics, copolyethylene/acrylic acid,polyurethane, a thermoplastic elastomers, a relatively low molecularweight polyester, linseed oil, a ricinoleate and combinations of any twoor more thereof.

The water-soluble resin can be a polyacrylate.

The lubricant for use in the process according to the present inventionis selected from at least one of the group consisting of ethyleneglycol, stearic acid, sodium stearate, glycerine and glycols.

Depending on the composition of the extrudate composition, the pH can beacid or alkaline. Where the process uses an acidic aqueous solution, thepH-value of the solution can be between 3 and 4. Desirably, acetic acidis used to acidify the solution.

Where the process uses an alkaline aqueous solution, the pH-value of thesolution can be between 8 and 9. Ammonia can be used to adjust the pH tothe alkaline side.

According to a further aspect, the invention provides a method oftreating exhaust gas emissions from internal combustion engines from avehicle, which method comprising contacting the exhaust gas with athree-way catalyst according to the invention. A temperature at whichthe exhaust gas contacts the catalyst is preferably >100° C., suchas >150° C., >175° C., >200° C., >225° C., >250° C., >275° C. or >300°C., Preferably, the temperature at which the exhaust gas contacts thecatalyst is <600° C., such as <550° C., <525° C. or <500° C.

According to a further aspect, the invention provides an exhaust systemfor an internal combustion engine, which exhaust system comprising athree-way catalyst according to the invention.

According to a further aspect, the invention provides a vehicle, e.g. anautomobile, comprising an internal combustion engine and an exhaustsystem according to the invention. In a preferred embodiment, theinternal combustion engine is a positive ignition engine, e.g. a sparkignition engine. Such engines are typically fuelled with gasoline fuel,but may also be fuelled with “alternative” fuel stocks including blendsof gasoline and ethanol etc.

EXAMPLES

In order that the invention may be more fully understood, the followingnon-limiting Examples are provided.

Example 1 Extruded Zeolite Monolith Substrate

An extruded zeolite monolith substrate was made according to methodssimilar to those disclosed in U.S. Pat. No. 7,507,684. Powderedcommercially available beta zeolite in hydrogen form is mixed with glassfibres, Kaolin filler and powdered synthetic boehmite (Pural SB) and isprocessed in an aqueous solution with a pH-value of 5-6 into a shapeableand flowable slip by admixture with cellulose (CMC-QP10000H), theplasticizer Zusoplast (a brand name of Zschimmer & Schwarz GmbH & Co KG)and the organic auxiliary agent PEO Alkox (a polyethylene oxide). Thequantitative proportions of the starting materials are selected in sucha way that the active material of the finished solid catalyst bodycontains 69% by weight of zeolite, 23% by weight of γ-Al₂O₃, 5% byweight of glass fibers and 3% by weight of Kaolin. The shapeable mixtureis extruded into a 1″ diameter×3″ long flowthrough honeycomb catalystbody, i.e. with continuous channels and with a circular cross-sectionexhibiting a cell density of 300 cpsi or 400 cpsi (cells per squareinch). Subsequently, the catalyst body is freeze dried for 1 hour at 2mbar according to the method described in WO 2009/080155 (the entirecontents of which is incorporated herein by reference) and calcined at atemperature of 580° C. to form a solid catalyst body.

Example 2 Single Layer Three-Way Catalyst on Extruded Zeolite SubstrateMonolith

To the 300 cpsi and 400 cpsi 1″×3″ extruded zeolite monolith substratesamples of Example 1 was washcoated a single layer of a three-waycatalyst composition comprising a mixture of a majority of γ-alumina anda mixed oxide of ceria-zirconia supporting palladium (in a majority) andrhodium using methods disclosed in WO 99/47260, the entire contents ofwhich are incorporated herein by reference, i.e. a method of coating amonolithic support, comprising the steps of (a) locating a containmentmeans on top of a monolithic support; (b) dosing a predeterminedquantity of a liquid component into the containment means, wherein theorder of steps (a) and (b) is (a) then (b) or (b) then (a); and (c)applying vacuum to draw the entirety of the quantity of the liquidcomponent into at least a portion of the monolithic support, andretaining all of the quantity of the liquid component within themonolithic support without recycle. The resulting product was dried andcalcined at 600° C.

Comparative Example 3 Two-Layer Three-Way Catalyst

A commercially available cordierite monolith substrate at 300 cpsi waswashcoated (according to the techniques in WO 99/47260) with a firstlayer comprising beta zeolite and a colloidal silica binder at 2.00 g infollowed by drying and calcination at 600° C. A second, three-waycatalyst layer according to Example 2 was applied in a washcoat as anoverlayer over the first beta zeolite layer. The resulting product wasdried and calcined at 600° C. A 1″×3″ core was cut from the coatedmonolith substrate.

Example 4 Three-Way Catalyst Testing

Catalyst samples of Example 2 and Comparative Example 3 were testedusing a laboratory synthetic catalyst activity test (SCAT) rig,according to the following steps:

-   -   (i) Lean pre-treatment at 500° C. in 5% O₂ in N₂ (balance) for        15 minutes and then cool down to 30° C. in N₂;    -   (ii) Establish baseline feed in a catalyst bypass at 16 L/min        (25K/h SV) of 0.15% HC (composed of toluene 17 vol %; isopentane        24 vol %; and propylene 59 vol %), 0.1% CO, 10% H₂O vapour and        balance compressed air;    -   (iii) Begin data collection and wait for 30 seconds;    -   (iv) Send HC feed to sample for a 30 second adsorption        maintained at 30° C.-40° C.;    -   (iv) Send gas feed via catalyst bypass;    -   (v) Remove air, HC and CO from feed, and rebalance with N₂ to        maintain 16 L/min;    -   (vi) Reintroduce gas feed to sample and ramp temperature from        30° C. to 550° C. at 40° C./min;    -   (vii) End data collection; cool-down to 30° C. with N₂ flow        through sample; and    -   (viii) Divert gas flow to bypass.

This test regime is also shown pictorially in FIG. 1, from which it canbe seen that the outlet temperature during the bypass step initiallyincreases beyond the inlet temperature but otherwise the inlet andoutlet temperatures are in step.

The results for catalyst samples of Examples 2 and Comparative Example 3are shown in FIG. 2, from which it can be seen that the catalyst samplesof Example 2 show significantly improved HC conversion (54% for the 400cpsi embodiment and 55% for the 300 cpsi embodiment compared to 46%)than the Comparative Example 3 sample.

Example 5 Extruded Zeolite Monolith Substrate

An alternative extruded zeolite monolith substrate to Example 1 was madeaccording to methods similar to those disclosed in U.S. Pat. No.7,507,684. Powdered commercially available beta zeolite in hydrogen form(Tosoh) is mixed with glass fibres (Vetrotex 4.5 mm (Saint-Gobain)), lowalkaline clay filler and powdered synthetic boehmite (Pural SB) and isprocessed in an aqueous solution with a pH-value of 5-6 into a shapeableand flowable slip by admixture with 8 wt % cellulose (based on the totalinorganic solids content) (CVP-M-5280 (Dow Wolff Cellulosics)). Thequantitative proportions of the starting materials are selected in sucha way that the active material of the finished solid catalyst bodycontains 60% by weight of zeolite, 25% by weight of clay, 7% by weightγ-Al₂O₃ and 8% by weight of glass fibres. The shapeable mixture isextruded into a flow-through honeycomb catalyst body, i.e. withcontinuous channels and with a circular cross-section in a desired celldensity. Subsequently, the catalyst body is freeze dried for 1 hour at 2mbar according to the method described in WO 2009/080155 (the entirecontents of which is incorporated herein by reference) and calcined at atemperature of 580° C. to form a solid catalyst body.

Example 6 Extruded V₂O₅/WO_(x)-TiO₂ Filter

A Reference extruded V₂O₅/WO_(x)-TiO₂ solid body was prepared similarlyto Examples 1 and 5 by blending components A, B, F and S as set out inTable 1 with water to make a kneadable paste. Additives H (poremodifiers) were added and the material was kneaded for 10 mins todisperse the pore modifiers. The resulting composition was extruded,dried and calcined as described in Examples 1 and 5. It should be notedthat the percentage quantities of inorganic solids present in the finalcalcined article is 100%. Quantities of additives (here H and S) thatare removed by combustion during calcination are provided in wt %relative to the 100% inorganic solids content.

TABLE 1 Active Extrusion Additional Components Binder StabilizerAdditive Additives A1 A2 B1 B2 B3 F1 H1 H2 H3 S1 S2 S3 82.90 1.70 3.003.00 1.40 8.00 1.00 1.00 0.30 1.76 9.20 0.56 A1 = TiW (98.9%, MCl0/Cristal) A2 = V₂O₅ from AMV (78% V₂O₅, GFE) B1 = Bentonite (90%,ACE/Mizuka) B2 = Kaolin (97.9% TK0177/Thiele) B3 = SiO₂ (100%,Tixosil/Novus) F1 = Glass fibers (Vetrotex 4.5 mm/Saint Gobain) H1 =Cellulose (QP10000H/Nordmann) H2 = PEO (Alkox/Airoko) H3 = Zusoplast(Zschimmer&Schwarz) S1 = MEA (Imhoff & Stahl) S2 = NH₃ S3 = C₃H₆O₃(Fauth)

The following pore modifiers were used instead of the ExtrusionAdditives H1, H2 and H3 in Table 1, with amounts shown being relative tothe total weight of inorganic solid in the recipe of Table 1.

TABLE 2 Wt % Used in Pore Volume Pore Radius Porosity Pore ModifierTable 1 Recipe (mm³/g) (Å) (%) Reference See Table 1 310.1 1783.6 39.8Cellulose CMC- 20 QP10000H (Nordmann) BC200 (Kremer 13 Pigmente GmbH &Co. KG) PAN Fibres 13 Recycling 9 333.6 1930.9 41.2 Arbocel 10 427 295047.2 (Schwarzwälder Textil-Werke) HOP Fibre 10 426 2629 48.8(Osthoff-Petrasch GmbH) Arbocel 15 524 5281 50.2 (SchwarzwälderTextil-Werke) HOP Fibre 15 543 3085 54.4 (Osthoff-Petrasch GmbH)

Porosity and pore volume and pore radius can be measured e.g. usingmercury intrusion porosimetry.

The results of Table 2 entries including pore volume and porosity arealso represented in FIG. 3. It can be seen from these results that theporosity and pore volume of the Reference can be increased byappropriate selection of pore modifiers so that an extruded solid bodymade using such pore modifiers may be used in the manufacture ofwall-flow filters.

These results are generic for increasing the porosity, pore volume etc.properties independent of the active components of the solid extrudedbody. That is, although increasing porosity and pore volume etc. of thisExample 6 are illustrated using V₂O₅/WO_(x)-TiO₂ active materials, theprinciples of increasing porosity and pore volume etc. disclosed in thisExample 6 are applicable to the extrusion of any active material, e.g.an extruded solid body for use in a gasoline soot filter comprising athree-way catalyst, because the pore modifiers are burnt out in thecalcination process leaving the active materials and fillers etc. behindas inorganic solids.

FIG. 4 compares the pore volume of a different Reference with solidextruded V₂O₅/WO_(x)-TiO₂ materials prepared using other pore modifiersset out in Table 2 compared also with a commercially available wallflowfilter (NGK). It can be seen from the graph that the inclusion of poremodifiers has improved the porosity and pore volume of the Referenceextruded solid body so that the materials have properties approachingthose of commercially available wall-flow filters.

Example 7 Extruded Catalysed Soot Filter

This is a prophetic example. A catalysed wall-flow filter monolithsubstrate can be prepared as follows. An appropriate amount of CeO₂—ZrO₂mixed oxide may be mixed with glass fibres, powdered synthetic boehmite(Pural SB) and beta zeolite and processed in an aqueous solution with apH-value of 3.5 into a shapeable and flowable slip containing 1.2 wt %cellulose (CMC-QP1000011), 1.0 wt % of the organic auxiliary agent PEOAlkox (a polyethylene oxide) and 13 wt % of a mixture of the poremodifiers Rettenmaier BC200 and polyacrylonitrile (PAN) fibres. Thequantitative proportions of the starting materials may be selected insuch a way that the active material of the finished solid catalyst bodycontains 25% by weight of CeO₂—ZrO₂, 15 wt % beta zeolite, 52% by weightof γ-Al₂O₃ and 8% by weight glass fibres. The shapeable mixture can thenbe extruded into a honeycomb catalyst body with continuous channels andwith a circular cross-section exhibiting a cell density of 300 cpsi(cells per square inch). Subsequently, the catalyst body can be freezedried for 1 hour at 2 mbar according to the method described in WO2009/080155 (the entire contents of which is incorporated herein byreference) and calcined at a temperature of 580° C. to form a solidcatalyst body. Typically, it would be expected that the resultingproduct would have a mean pore size of approximately 10 μm.

The extruded flow-through monolith substrate comprising a plurality ofchannels may be made into a wall-flow filter arrangement whereby aplurality of first channels is plugged at an upstream end and aplurality of second channels not plugged at the upstream end are pluggedat a downstream end, wherein the arrangement of the first and secondchannels is such that laterally and vertically adjacent channels areplugged at opposite ends in the appearance of a checkerboard byinserting substantially gas impermeable plugs at the ends of thechannels in the desired pattern according to EP 1837063 (the entirecontents of which is incorporated herein by reference). This filterarrangement is also disclosed in SAE 810114 (the entire contents ofwhich is incorporated herein by reference). The calcined extrudedmonolith substrate can be coated with a washcoat comprising Pt—Rhaccording to the methods disclosed in WO 99/47260 or PCT/GB2011/050005filed on 4 Jan. 2011. The latter method comprises the steps of: (i)holding a honeycomb monolith substrate substantially vertically; (ii)introducing a pre-determined volume of the liquid into the substrate viaopen ends of the channels at a lower end of the substrate; (iii)sealingly retaining the introduced liquid within the substrate; (iv)inverting the substrate containing the retained liquid; and (v) applyinga vacuum to open ends of the channels of the substrate at the inverted,lower end of the substrate to draw the liquid along the channels of thesubstrate.

For the avoidance of any doubt, the entire contents of any and alldocuments cited herein are incorporated herein by reference.

1. A three-way catalyst comprising an extruded solid body comprising:10% by weight of at least one binder/matrix component; 5-90% by weightof a zeolitic molecular sieve, a non-zeolitic molecular sieve or amixture of any two or more thereof; and 0-80% by weight optionallystabilised ceria, which catalyst comprising at least one precious metaland optionally at least one non-precious metal, wherein: (i) the atleast one precious metal is carried in one or more coating layer(s) on asurface of the extruded solid body; (ii) at least one metal is presentthroughout the extruded solid body and at least one precious metal isalso carried in one or more coating layer(s) on a surface of theextruded solid body; or (iii) at least one metal is present throughoutthe extruded solid body, is present in a higher concentration at asurface of the extruded solid body and at least one precious metal isalso carried in one or more coating layer(s) on the surface of theextruded solid body.
 2. A catalyst according to claim 1, wherein the atleast one metal is associated with the zeolitic molecular sievecomponent, the non-zeolitic molecular sieve component or either or bothof the zeolitic molecular sieve component and the non-zeolitic molecularsieve components in the mixture.
 3. A catalyst according to claim 2,wherein the extruded solid body comprises at least one first metalassociated with the zeolitic molecular sieve component, the non-zeoliticmolecular sieve component or either or both of the zeolitic molecularsieve component and the non-zeolitic molecular sieve components in themixture and at least one second metal that is not associated with thezeolitic molecular sieve component, the non-zeolitic molecular sievecomponent or either or both of the zeolitic molecular sieve componentand the non-zeolitic molecular sieve components in the mixture. 4.(canceled)
 5. A three-way catalyst according to claim 1, wherein theprecious metal is selected from the group consisting of Pt, Au, Ag, Ir,Ru, Rh, Pd and Os. 6.-8. (canceled)
 9. A three-way catalyst according toclaim 1, wherein: the at least one binder/matrix component is selectedfrom the croup consisting of cordierite, nitrides, carbides, borides,intermetallics, lithium aluminosilicate, an optionally doped alumina, asilica source, titania, zirconia, titania-zirconia, zircon and mixturesof any two or more thereof; and the zeolitic molecular sieve, thenon-zeolitic molecular sieve or the mixture of any two or more thereofeach optionally contain one or more metal; and the extruded solid bodyfurther comprises: 0-80% by weight of spinel; and 0-25% by weightinorganic fibres.
 10. A three-way catalyst according to claim 1, whereinthe extruded solid body consists essentially of: the at least onebinder/matrix component; the zeolitic molecular sieve, the non-zeoliticmolecular sieve or the mixture of any two or more thereof in an amountof 50-90% by weight; and 0-25% by weight of inorganic fibres, whereinthe at least one binder/matrix component is selected from the groupconsisting of cordierite, nitrides, carbides, borides, intermetallics,lithium aluminosilicate, a spinel, an optionally doped alumina, a sourceof silica, titania, zirconia, titania-zirconia, zircon and mixtures ofany two or more thereof; the zeolitic molecular sieve, the non-zeoliticmolecular sieve or the mixture of any two or more thereof eachoptionally contain one or more metal.
 11. A three-way catalyst accordingto claim 1, wherein the extruded solid body consists essentially of: theat least one binder/matrix component; the zeolitic molecular sieve, thenon-zeolitic molecular sieve or the mixture of any two or more thereofin an amount of 5-50% by weight; the optionally stabilised ceria in anamount of 20-80% by weight; and 0-25% by weight of inorganic fibres,wherein the at least one binder/matrix component is selected from thegroup consisting of a cordierite, nitrides, carbides, borides,intermetallics, lithium aluminosilicate, an optionally doped alumina, aspinel, a silica source, titania, zirconia, titania-zirconia, zircon andmixtures of any two or more thereof; the zeolitic molecular sieve, thenon-zeolitic molecular sieve or a the mixture of any two or more thereofeach optionally contain one or more metal.
 12. A three-way catalystaccording to claim 1 in the form of a wall-flow filter.
 13. (canceled)14. A three-way catalysed soot filter comprising an extruded solid bodyin the wall-flow filter configuration, which extruded solid catalystbody consisting essentially of: 15-70% by weight of cordierite,nitrides, carbides, borides, intermetallics, lithium aluminosilicate, aspinel, an optionally doped alumina, titania, zirconia,titania-zirconia, zircon and mixtures of any two or more thereof; 0-20%by weight of a source of silica; 5-50% by weight of a zeolitic molecularsieve, a non-zeolitic molecular sieve or a mixture of any two or morethereof, each optionally containing one or more metal; 20-80% by weightoptionally stabilised ceria; and 0-20% by weight of inorganic fibres,which extruded solid catalyst body being coated with one or morelayer(s) comprising supported at least one precious metal andcombinations of any two or more precious metals.
 15. A three-waycatalyst according to claim 1 comprising the extruded solid body in theflow-through configuration, wherein the extruded solid body consistsessentially of: the at least one binder/matrix component; the zeoliticmolecular sieve, the non-zeolitic molecular sieve or the mixture of anytwo or more thereof in an amount of 50-81% by weight; and 0-20% byweight of inorganic fibres, wherein the at least one binder/matrixcomponent comprises 15-30% by weight of cordierite, nitrides, carbides,borides, intermetallics, lithium aluminosilicate, a spinel, anoptionally doped alumina, titania, zirconia, titania-zirconia, zirconand mixtures of any two or more thereof; and 0-20% by weight of a sourceof silica; the zeolitic molecular sieve, the non-zeolitic molecularsieve or the mixture of any two or more thereof; each optionally containone or more metal; and the extruded solid catalyst body is coated with asingle layer comprising a mixture of a majority of γ-alumina and astabilised ceria supporting palladium only, a mixture of palladium andrhodium, a mixture of platinum and rhodium or a mixture of platinum,palladium and rhodium. 16.-21. (canceled)
 22. A three-way catalystaccording to claim 1, wherein the zeolitic molecular sieve, thenon-zeolitic molecular sieve or the mixture of any two or more thereofis selected from the group consisting of ZSM-5, beta, ferrierite andmixtures of any two or more thereof.
 23. A three-way catalyst accordingto claim 1, wherein the zeolitic molecular sieve, the non-zeoliticmolecular sieve or the mixture of any two or more thereof is analuminosilicate zeolite having a silica-to-alumina ratio of 10 orgreater. 24.-26. (canceled)
 27. A three-way catalyst according to claim1, wherein the at least one metal present in each of: (a) throughout theextruded solid body; (b) present in a higher concentration at a surfaceof the extruded solid body; and (c) carried in one or more coatinglayer(s) on a surface of the extruded solid body in features (ii) or(iii) is different from the at least one metal present in the otherlocation(s).
 28. A three-way catalyst according to claim 1, wherein theat least one metal is associated with the zeolitic molecular sievecomponent, the non-zeolitic molecular sieve component or either or bothof the zeolitic molecular sieve component and the non-zeolitic molecularsieve components in the mixture.
 29. A three-way catalyst according toclaim 28, wherein the or each at least one metal associated with thezeolitic molecular sieve, non-zeolitic molecular sieve or both molecularsieves in the mixture of any two or more thereof contains one or moremetal selected from the group consisting of a transition metal, alanthanide or a mixture of any two or more thereof.
 30. A three-waycatalyst according to claim 29, wherein the one or more metal is thetransition metal and the transition metal is selected from the groupconsisting of Cu, Pd, and Ag.
 31. (canceled)
 32. A process ofmanufacturing a three-way catalyst comprising the steps of: forming asolid extruded body by mixing powdered starting materials of: at leastone binder/matrix component or a precursor of one or more thereof;zeolitic molecular sieve, non zeolitic molecular sieve or a mixture ofany two or more thereof which zeolitic molecular sieve, non-zeoliticmolecular sieve or mixture of zeolitic and non-zeolitic molecular sievesbeing optionally associated with at least one metal; an optionaloptionally stabilised ceria; and an optional at least one metalcompound; with optional inorganic fibres; optionally adding an organicauxiliary agent; processing by mixing and/or kneading in an acid oralkaline aqueous solution optionally containing a metal salt of at leastone metal into a plastic compound to form a mixture; extruding themixture into a catalyst body, drying the catalyst body and calcining toform a solid extruded body; selecting quantitative proportions of thestarting materials such that the solid extruded body comprises 10% byweight of at least one binder/matrix component; 5-90% by weight of azeolitic molecular sieve, a non-zeolitic molecular sieve or a mixture ofany two or more thereof; and 0-80% by weight optionally stabilisedceria, and coating a surface of the solid extruded body with at leastone coating layer(s) containing at least one precious metal andoptionally also impregnating a surface of the solid extruded body withat least one metal.
 33. A method of treating exhaust gas emissions frominternal combustion engines from a stationary source or a vehicle,wherein said exhaust gas has HC, CO, and NO_(x), which method comprisingoxidizing the HC and CO and reducing the NO_(x) by contacting theexhaust gas with a three-way catalyst according to claim
 1. 34. Anexhaust system for an internal combustion engine, which exhaust systemcomprising a three-way catalyst according to claim
 1. 35. A vehiclecomprising an internal combustion engine and an exhaust system accordingto claim 34.